Effect of propranolol treatment on bone mass, bone mineral content, bone remodelling, parathyroid function and vitamin D metabolism in hyperthyroidism.

The effect of propranolol 160-640 mg/day for 3 months on the accelerated loss of bone matrix and mineral in hyperthyroidism was studied in seventeen patients. A rise in serum thyroxine (P less than 0.01) during the first 3 weeks was followed by a fall (P less than 0.02). Serum triiodothyronine declined during the study (P less than 0.02). The enhanced bone mineral mobilization and collagen turnover continued during treatment and the bone mineral content decreased 3.2% (P less than 0.01). The secondary adaptive changes in serum parathyroid hormone and vitamin-D metabolites and in renal phosphate handling stayed unchanged. Iliac crest bone biopsies after tetracycline double-labelling showed initially a high bone turnover (P less than 0.01) with a reduced amount of cortical and trabecular bone (P less than 0.05). Following treatment bone formation rate decreased at both cellular and tissue level (P less than 0.01). No significant changes were observed in the amount of cortical and trabecular bone. The investigation shows that propranolol, in contrast to antithyroid medication, lacks any curative effect on the accelerated bone loss in hyperthyroidism.